Mobile industry processor interface (MIPI) standards, embedded DisplayPort (eDP), and other standards have been set for image data and control signals of display devices. In accordance with such a standard, communication is performed between a host (e.g., an application processor) and a timing controller (also called a display driver IC). Furthermore, panel self-refresh (PSR) technology has been proposed to reduce electric power required for communication.
A technique for using an oxide semiconductor transistor (hereinafter, referred to as an OS transistor) for a display device such as a liquid crystal display or an organic electroluminescence (EL) display has attracted attention. An OS transistor has an extremely low off-state current. In some disclosed techniques, by utilizing this fact, the refresh frequency at the time of displaying still images is reduced and power consumption of liquid crystal displays or organic EL displays is accordingly reduced (Patent Document 1 and Patent Document 2). Note that the aforementioned technique for reducing the power consumption of the display device is referred to as idling stop in this specification.
An example in which an OS transistor is used for a nonvolatile memory device has been disclosed in Patent Document 3, where the extremely low off-state current of the OS transistor is utilized.